This invention concerns a method of exposing film in a vector film recorder while enabling efficient control of intensity, color, and line width. A copending application no. 889,035 entitled "METHOD FOR ENHANCEMENT OF DISPLAY SCREEN RESOLUTION" filed July 22, 1986, describes a related method of improving resolution.
Color film recorders are devices used to record electronic signals such as computer generated graphics on slide film, photographic film, or instant photographic film, and are often used as computer peripherals. An image to be film recorded is generated by a cathode ray tube (CRT) in a system closed with respect to light. The CRT in vector film recorders generates a series of lines drawn between endpoints to create an image. A color filter wheel, having filters for the three primary colors of light--red, green, and blue, controlled by a stepper motor filters the white light of the CRT to define the color for the image.
In some prior art film recorders, the amount of light reaching the film, and the subsequent exposure, was controlled by the intensity of the image generated by the CRT, which was dependent on the voltage of the electron beam used to generate the line. However, an increase in intensity also caused an increase in the width of the line generated on the CRT. Furthermore the relationship of the intensity to the voltage of the electron beam was not a linear function. Special hardware was also required to vary the intensity. These problems made it difficult to control the intensity, line width, and color of the image generated by the CRT and therefore difficult to control the quality of the recorded image.